Over the years there have been a number of connector devices and fittings provided for attaching conduit, cable, cord and similar flexible members to electrical outlets, junction boxes, panels and the like. The most commonly used connectors include a locking nut which secures the connector to the electrical box by threaded interaction with an externally threaded male portion which is pushed through a knockout or hole in the electrical panel. Examples of clamping devices utilizing a threaded nut within the electrical box to attach the device to the box include those shown in U.S. Pat. Nos. 2,858,358 (which issued to W. Hawke) and 4,250,348 (which issued to H. Kitagawa). Particularly, Hawke contemplates screwing its clamp body A into the wall of a switch casing or other fitting, with further securement by a locknut within the switch casing if desired. Similarly, the Kitagawa clamping device includes a cylinder formed with threads corresponding with internal threads of a nut which may be used to fix the body on a wall plate. While the Hawke patent does not illustrate any means for sealing its clamp body adjacent the wall of a switch casing, Kitagawa provides that its annular flange may be formed with a small projection, or that a washer may be disposed on the side of the flange falling in contact with the wall plate for providing a fluid-tight connection. The Hawke clamping gland further requires the cutting back of the outer sheath and armor of a flexible electrical cable prior to engagement with a subassembly which fits into the clamp body. Thereafter, a cover member is screwed upon the clamp body to secure the multi-piece subassembly therewithin and to clamp the cable in place. The Kitagawa clamping device includes a plurality of elastic legs having projections on their distal ends and a cylindrical packing ring which bind against a cable held within the clamping device when a threaded clamping pipe is tightened onto the lower portion of the clamping device.
Because electrical boxes and panels are often relatively small and/or house a plurality of other wires, cables, and connectors, it is often quite difficult to secure a locking nut onto the male portion of a connector inserted into that electrical box, as required by these prior art devices. Cross-threading of the lock nut on the threaded male portion of the connector, and the inherent difficulty in applying a tightening tool to the lock nut and connecting device, resulted in difficult installations and often loose connections. As the electrical conduit, connector, and electrical box are often part of an electrical grounding path, loose lock nuts and connections can present serious safety hazards such as shock, electrocution, malfunction, and/or fire.
Another prior fitting for flexible conduit having many of these same shortcomings is described in U.S. Pat. No. 3,006,664 (which issued to A. Appleton et al.). Particularly, the Appleton fitting includes a thin annular end portion adapted to be inserted into an aperture of an electrical box. Once inserted into the box, the annular end must be spun or peened to form a bead capable of securely holding the fitting body in the box. While the Appleton et al. fitting includes an inner sleeve formed with spiral threads to interact with the structural groove within an electrical conduit to be connected, and a sealing nut which slips over the end of a conduit and bends a flange on the inner sleeve against the conduit when tightened into place, the annular end portion which must be formed after insertion into an electrical box will require inconvenient spinning or peening forming operations after insertion along with all of the other problems described above.
Other coupling devices, such as shown in U.S. Pat. No. 1,106,761 (which issued to A. Weikert, et al.), avoid a need for use of lock nuts or inconvenient attachment operations by providing a plurality of spring grippers formed in a longitudinally split blank of metal. In conjunction with an adjustable collar which rotatably surrounds the central portion of the connector body, the Weikert et al. device provides a locking means which does not require the post-insertion attachment of a locking nut within the electrical box. Weikert et al., however, require a large number of parts which must be assembled, including a separate band which is to be tightened by a bolt/nut combination about a plurality of gripping devices for locking the coupling to the conduit.
Another snap-in device is shown in U.S. Pat. No. 3,285,551 (which issued to A. Tschanz), which includes a tubular body having a forward tapered portion with a plurality of slots to enable insertion into an opening in an electrical box. An outwardly extending flange can be provided in a spring-like manner to firmly hold the body in an opening of the electrical box once inserted. The rear portion of the tubular body is also slotted and tapered, whereby an internally threaded nut having an inner tapered surface can be tightened onto the tubular body to bind the slotted/tapered portion onto flexible conduit held therewithin. The Tschanz assembly, however, relies upon careful dimensional tolerance of the assembly itself to establish and maintain a sealing fit with the aperture of an electrical box. Variations in manufacturing accuracy and field conditions can provide sizable margins of error resulting in improper or loose connections.
The feed-through device of U.S. Pat. No. 4,234,218 (which issued to A. Rogers) includes a first tubular member having integral deformable segments which can be pushed through an aperture in an electrical box and which spring back to their original configuration once inserted. A non-deformable heat recoverable member is then inserted within the first tubular member to prevent the deformable segments from thereafter being deformed inwardly. The heat recoverable insert is thereafter shrunk fit onto a cable to form a pressure tight seal. Such a heat shrinkable connecting device cannot, by itself, provide an electrical grounding path. Consequently, in addition to requiring the application of heat as part of the connection procedure, additional grounding structure and assembly may be required in many circumstances.
U.S. Pat. No. 4,468,535 (which issued to J. Law) also discloses a liquid-tight connector designed to be snapped into the opening of an electrical box or the like. However, as described above with respect to the Tschanz device, the Law connector inherently relies upon close manufacturing tolerances and a sealing washer to provide its liquid-tight connection. Additionally, while the Law structure includes a metallic grounding ferrule to provide electrical connection between the conduit being connected and the electrical enclosure, and provides a helical outer edge which can be screw-threaded into the inside wall of the metallic conduit, arrangements such as this require relatively careful preparation of the cut end of a metallic sheathed cable to be connected in order to provide relatively smooth surfaces for sealing within the internal portions of the connector. Preparation of the end of the conduit to be connected would add to the labor and inconvenience required in utilizing such a connector.
Another connector which does not require the application of a locking nut after insertion of the connector to an outlet box is shown in U.S. Pat. No. 1,131,399 (which issued to J. McGinley). Particularly, the McGinley arrangement contemplates the provision of an outlet box with a specially notched cutout to correspond with outwardly extending lugs formed on a coupling. The coupling lugs are inserted into the notched cutouts, then the coupler is rotated to lock the device into the opening between its flange and the lugs. This arrangement, however, requires use of special outlet boxes including notched openings, and also relies upon the coupling remaining in its rotated position to maintain the locked condition. In use, cables and their connectors are often subjected to movement and stress, including rotational forces which could cause the McGinley coupling to become disconnected from the outlet box.
As can be seen, while a wide variety of connectors have been provided and directed to achieving liquid-tight connections for conduits, cables, cords and the like, heretofore there has not been available a relatively universally applicable connector for conduits which can provide a reliable fluid-tight connection from the outside of an aperture, and which is easy to use and which can withstand the rigors of installation and service commonly encountered in the industry.